Jurnal Rekayasa Geofisika Indonesia

Subsurface Interpretation And Structure Delineation Of The Muna-Buton Basin Based On Satellite Gravity Data

Muhammad Nur Ahsan Zakir, Wawan Gunawan Abdul Kadir, Eko Januari Wahyudi — Thu, 21 Dec 2023 00:00:00 +0000

Island of Buton is a region located in the Southeast Sulawesi region, Indonesia. The formation of Buton Island is the result of intense tectonic processes, resulting in diverse geological resources, including natural resources such as oil and natural gas accumulated in a sedimentary basin. Gravity field measurements have been conducted to interpret subsurface structures in the Muna-Buton Basin. The data used consist of free air gravity anomaly data, requiring corrections for Bouguer and terrain to obtain a complete Bouguer anomaly. Anomaly separation is performed using trend surface analysis method. Gradient analysis is conducted on residual anomalies to delineate basin structures in the research area using several methods, including horizontal gradient, total gradient, tilt-angle horizontal gradient, and improved logistic filter. Qualitatively, two sub-basins can be delineated: Sub-basin A is in the east and sub-basin B is in the west. Sub-basin A is estimated to be the Bulu sub-basin, while sub-basin B is the Buton Strait sub-basin. Based on subsurface modeling results, there is a basement layer indicated to be at an estimated shallowest depth of 2 km in the Buton Strait sub-basin and an estimated shallowest depth of 3 km in the Bulu Basin sub-basin. The depth of this basement layer increases towards the center of the basin, reaching more than 4 km.

Simulation of Significant Wave Height in The Makassar Strait in January-February 2016

Thu, 21 Dec 2023 00:00:00 +0000

Knowledge of the characteristics of sea waves is very important for many maritime fields such as shipping safety, offshore industry, coastal area development, defense, and ship design. As the largest maritime country in the world, Indonesia is vulnerable to high sea waves. BMKG adopts the third generation wave model, namely WAVEWATCH-III which was developed by NOAA, USA. This model is used to predict the height and direction of sea waves in Indonesian waters. The purpose of this study is to determine the characteristics of the results of the WAVEWATCH-III wave model in the Makassar Strait. In January-February 2016 significant sea wave heights ranged from 0 m to 1.5 m and the direction of the waves came from the northeast in the Makassar Strait. Significant wave heights in January-February 2016 were not at a level that endangered shipping lanes in the Makassar Strait area.

Keywords: Ocean Waves, Makassar Strait, Wave Model.

Analysis of The Thickness of The Sediment Layer using The Horizontal to Vertical Spectral Ratio (HVSR) Method in The Coastal Area of Moramo District, South Konawe District

Sun, 24 Dec 2023 00:00:00 +0000

Research has been carried out in the coastal area of Moramo District, South Konawe Regency. This study aims to determine the value of the distribution of sediment layer thickness. Data collection was carried out using a TDL-303S seismometer at 15 measurement points. Microtremor data were analyzed using the HVSR method (Horizontal To Vertical Spectral Ratio) use software geopsy 3.4.2 to obtain the dominant frequency value (f₀) which then determines the value of the wave velocity shear (VS30) to obtain the value of the thickness of the sediment layer (h). The results of data analysis obtained the dominant frequency value (f₀) obtained ranged from 1.025 Hz to 14.297 Hz and the wave speed values shear (V_S30) obtained from website www.USGS.gov with a range of values ranging from 234.43 m/s to 422.33 m/s. Based on the data obtained, the value of the distribution of sediment layer thickness (h) will be determined. The thickness of the sediment layer in the study area ranged from 6.596 meters to 66.124 meters.

Analysis Of Limestone Occurrence Using Resistivity Method In Block A Of PT Graha Batu Perdana Mining Area Bungku Pesisir Sub-District Morowali District

Tesalonika Mangnga Tolan, Jahidin Jahidin, Erzam Salahudin Hasan — Sun, 24 Dec 2023 00:00:00 +0000

This research was conducted to determine the resistivity values and the presence of limestone in Block A of PT Graha Batu Perdana mining area, Bungku Pesisir Subdistrict, Morowali Regency, using the Wenner-Schlumberger resistivity method. This study utilized secondary data and falls under the category of data processing studies, with measurements conducted along 4 traverses, each with a length of 310 m. The data obtained consisted of potential difference values and current strength, which were then processed using Microsoft Excel to obtain resistivity values. Subsequently, a 2D processing was carried out using res2Dinv to generate a 2D cross-section, which was then interpreted to identify subsurface conditions based on resistivity values. The distribution of limestone in the research area along 4 traverses is as follows traverse 1 had a resistivity value of 694 Ωm with a thickness of 30,14 m, traverse 2 had resistivity values ranging from 1089 to 2350 Ωm with thinknesses between 28,15 and 43,14 m, traverse 3 had resistivity values ranging from 544 to 15108 Ωm with thinknesses between 1,25 and 39,4 m, traverse 4 had resistivity values ranging from 710 to 3325 Ωm with thinknesses between 38,15 m.

Analysis of Heavy Metal Concertrations of The Soil Surface Based on The Magnetic Susceptibility Values on The Coast Of Lasolo Bay and Surrounding

Aziza Nur Aziza, Irawati Irawati, Erzam Salahudin Hasan — Wed, 27 Dec 2023 00:00:00 +0000

This research is located in Lasolo Bay, that is at Tapuemea Village, Molawe District, North Konawe Regency. The purpose of the study was to determine the concentration of heavy metals based on magnetic susceptibility values using X-Ray Fluorescence (XRF) and determine sediment quality. The results of XRF measurements showed that the highest concentrations of heavy metals for mining zones, coastal zones and residential zones were Nickel (Ni), Iron (Fe) and Cobalt (Co), while heavy metals that did not exceed the maximum threshold were Copper (Cu) and Zinc (Zn). Sediment quality as seen from the Pollution Load Index (PLI) analysis is included in the polluted category with a geoaccumulation index value indicating that there has been pollution with moderate to extremely severe pollution categories.

Effectiveness of The Peter Half Slope Method in Determining The Depth of Anomalous Objects

Sun, 07 Jan 2024 00:00:00 +0000

The Peter Half Slope method is one of several techniques that can be used as the earliest quantitative depth determination. It is hoped that through this research the literature on the Peter Half Slope method can increase. This research aim is to prove the effectiveness of the Peter Half Slope method in estimating the depth of subsurface anomalous objects through comparison of models (synthesis) that have not and have been added random values as error values. This research begins with modeling in Geomodel software. After obtaining the appropriate synthetic modeling results, the next step is to perform processing in Matlab software to test the effectiveness of the Peter Half Slope method. After entering all the values, the average value of the anomalous depth of model 1 in d1, d2, and d3 is 100.1890m. As for model 2, the average value of model 2 anomaly depth is 97.35344m. The error between the original modeling and the modeling added random values using the Peter Half Slope method is 2.83%. Thus, this method is considered effective in determining the depth of subsurface anomalies through magnetic response, but to determine the exact depth requires the use of other methods as the main method.